Current methods for treating or processing animal skin substrates can necessitate the use of vast quantities of water. For example, in treatment methods wherein the animal skin substrate comprises a hide, typically 30 kg of water is required per kg of hide. Large volumes of water can be needed in order to remove unwanted materials from the animal skin (such as those that are liable to decomposition) and also in subsequent steps of the process which involve chemical modification to confer certain properties on the substrate. Chemical modification of the substrate can be carried out for the purpose of, inter alia, preserving, waterproofing, colouring and/or providing any desired textural or aesthetic qualities. The various steps described above will generally be performed in the presence of a treatment formulation comprising one or more components.
Due to the large amounts of water relative to the weight of animal substrate, current treatment processes known in the art also require a proportionate quantity of chemicals used in the treatment formulation to ensure an effective treatment of the substrate within an acceptable timeframe. Consequently, excessive amounts of polluting and environmentally damaging effluents can be produced from such processes. Furthermore, long process times are necessary.
Many of the methods for preparing animal skin substrates for human use still remain predominantly based on traditional processes and there have been few advances in recent years. For example, methods for the processing and manufacturing of leather have remained largely unchanged for 75 years. EP0439108 filed in 1991 and directed to a process using carbon dioxide for deliming of hides, discloses an example of one of the few recent developments in this field.
Prior to the innovations disclosed herein, the inventors have previously addressed the problem of reducing water consumption in a domestic or industrial cleaning method. Thus, in WO-A-2007/128962 there is disclosed a method and formulation for cleaning a soiled substrate, the method comprising the treatment of the moistened substrate with a formulation comprising a multiplicity of polymeric particles, wherein the formulation is free of organic solvents. The soiled substrate may be wetted so as to achieve a substrate to water ratio of between 1:0.1 to 1:5 w/w, and optionally, the formulation may additionally comprise at least one cleaning material, which typically comprises a surfactant, which most preferably has detergent properties. The soiled substrate may comprise a textile fibre. The polymeric particles may, for example, comprise particles of polyamides, polyesters, polyalkenes, polyurethanes or their copolymers, a particular example being nylon beads.
Following the development of this method the present applicant further devised an apparatus specially adapted to clean soiled substrates by virtue of recirculation of the polymeric particles. Thus, in WO2011/098815, the present applicant provided an apparatus for use in the cleaning of soiled substrates, the apparatus comprising housing means having a first upper chamber with a rotatably mounted cylindrical cage mounted therein and a second lower chamber located beneath the cylindrical cage, and additionally comprising at least one recirculation means, access means, pumping means and a multiplicity of delivery means, wherein the rotatably mounted cylindrical cage comprises a drum having perforated side walls where up to 60% of the surface area of the side walls comprises perforations comprising holes having a diameter of no greater than 25.0 mm.
Although the method and apparatus disclosed in WO2007/128962 and WO2011/098815 provided considerable improvements for the cleaning of soiled substrates these developments were primarily applicable to the field of laundry wherein the substrate typically comprises textile fibre garments. The method and apparatus of WO2007/128962 and WO2011/098815 (so-called “bead cleaning” technologies) were not however specifically adapted or optimised for the treatment of animal skin substrates.
The present disclosure therefore seeks to provide an apparatus and method for use in the treatment of animal skin substrates that can ameliorate or overcome the above-noted problems associated with the prior art. Particularly, there is desired a method and apparatus for treating an animal skin substrate which requires less water than the processes of the prior art and that reduces the volume of polluting and hazardous effluent produced. Furthermore, there is desired a method and apparatus for treating an animal skin substrate with a solid particulate material that provides an effective means of separating the solid particulate material from the substrate.